Thermal cut-out.



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uw O Tq Nw Ee w@ IJ #www D MTESSES To all whom it may concern:

Be it known that l, ERNST J. BERG, a citizen of the United States, residing at Schenectady, in the county of Schenectady and State of N ew York, have invented certain new and `useful Improvements in Thermal Cut-Outs,

of which the following is a specification.

The present invention relates to thermal cut-out devices for protecting electrical apparatus from the injurious action of excessive or abnormal currents and more especially to the so-called multiple-fuse type of such devices. y y

As is well known, the multiple-fuse type of cut-out usually comprises a prima-ry fuse having a low meltingoint and large currentcarrying capacity an a secondary fuse connected in parallel therewith and having a relativelyhighmelting-point and low currentc fr capacity. 'When the current rises gradua y above the normal, the primary fuse melts first, but instead of the current arcing across between the severed ends thereof through the ases of volatilization, as is usual where a sing e fuse is employed, it passes by way of the secondary fusewhich moment arily resiststhe melting action of t-he excess current and then breaks without forming gases to carry the arc.

It has been found, however, that where eX- cessive current is applied to a circuit suddenly, as bylightning or a short-circuit, the time `element required toheat up the two fuses is such that the secondary will melt either before or concurrently with the primary, and

ple-fuse arrangement over t e ordinary single fuse.

The object of my invention is to provide a p multiple-fuse cut-out with means for causing the growth of current to lag in the secondary fuse sufficient to insure the advance rupture of the primary fuse.

The invention will -be readily understood upon reference to the following description, taken in connection with the accompanying drawings, forming a part of this specification, inwhich- A Figure 1 is a lan of a multiple-fuse arrangement embo one form of my inven- En sauras ERNST a. BERG, er scHENEcrADnNEi-v YORK, AssIGNoR TOGEERL ELECTRIC coi-train', A conPoRATIoN or New roiur. y,

THERMAL CUT-ouv.,

Specification of Letters Patent.

Application filed .im 1,1903. smurf.. 159,512.

thereby nullify the advanta es of the multi- QFFIGE.

Patented Nov. 6, 1906.

tion. Fig. 2 is a right-hand elevation thereof. Fig. 3 is a central transverse section, and Eig. 4 is a conventional diagramv of connectlons.

In the arrangement shown in the drawings the primary and secondary fuses A and B are mounted upon a common support or base C, of insulating material, by means of ordinary metallic clips provided with binding-posts l, 2,3, and 4. An induction-coil D, having a. tubular iron core 5 is, for convenience, supported by the inclosing casing of the secondary fuse B and has its ends connected, respectively, to one end of the main circuit-conductor E at the binding-post 2 and to the end of the secondary fuse B at the bindinG-post at. The other ends of t-he fuses arejoined by a connector-wire 6, secured to binding-posts 1 and v 3, to one ofwhich the other end of the main circuit-conductor E is secured. Thus, as indicated in Fig. 4, the secondary fuse B and its series-connected induction-coil D are connected in multiple with the primary fuse A., so thatunder normal working conditions a part of the current traverses the primary fuse and a part the secondary fuse and its coil D, producing substantially the same degree of temperature in bot-h fuses; but when the amount of current in the main circuit is suddenly increased the How in t-he primary fuse is correspondingly increased and its temperature suddenly raised t-o t-he point of melting, whereasthetendency of the flow of current to increase through the secondary fuse B is momentarily checked by the inductive action of the coil D thereon, so that the rise in temperature in the secondaryfuse is causedto lag relatively to that of the primary fuse A, thereb the advance rupture of the latter ii'ise. l

The fuses shown in the drawings are ofthe usual cartridge typewith a filling of sand or powdered insulating material. The fusible conductor 7 of the primary fuse A is a soft metalwith a relatively low melting point, While the fusible conductor 8 of the second,- ary fuseB is harder, with a hivher meltingpoint and practically non-volatile.

I do not desire to be restricted to the condescribed, for itis apparent that they may be changed and modiiied Without departing from my invention.

What I claim as new, and desireto secure by Letters Patent of the United States, is-

1. In a multiple-fuse arrangement, the combination with onemof the fuses, of means for causing the current to vary less rapidly therein than in the other fuse.

2. In a multiple-fuse arrangement, the combination With one of the uses, of electroreactive means to cause the current to vary less rapidly therein than in the other fuse.

3. In a multiple-fuse arrangement, the combination With one of the fuses, of an inducance device connected in series there- Wit 4. The combination of a fuse having an inductance device connected in series therewith, and a second fuse connected in multiple With the first fuse and its induct ance device..

5. The combination of a fine-Wire fuse, an induction-coil connected in series therewith, and a primary use connected in multiple with the fine-Wire fuse and its induction-coil. 6. A thermal cut-out comprising a fusible member, and an iron core and an induct ancecoil surroundimg,r said member. i y

7. A thermal cut-out comprising a fusible member having an inclosing casing, a tubular iron core about said member, and an inductance-coil Wound upon said core.

In Witness whereof I have hereunto set my hand this 29th dayof May, 1903.

ERNST BERG. Witnesses:

BENJAMIN B. HULL, HELEN URFORD. 

